JPH051132Y2 - - Google Patents

Description

[Detailed description of the invention] This invention is a high-frequency amplifier, in particular, the equivalent circuit viewed from the output side to the input side forms a bridge T-shaped trap circuit, which increases the attenuation from the output side to the input side. The present invention relates to a high frequency amplifier configured as described above.

The technical background of the present invention will be explained based on FIG. Figure 1 shows the booster/TV receiving equipment.
Mixer 1 is shown. In this booster mixer, the video signal received by the antenna 2 passes through the antenna input terminal 3, the filter 4, the booster 5, the distributor 6, the attenuator 7, the booster 8, the attenuator 9, and the booster 10. )11. A signal is supplied to the mixer 11 from the RF modulator 12 via the modulator input terminal 13, and is mixed with the video signal from the booster 10.
The signal is supplied to the television receiver 15 via the television receiver output terminal 14. The video signal received by the antenna 2 is distributed by a distributor 6, passes through an attenuator 16, a booster 17, an attenuator 18, and then is sent to a recording output terminal 19.
is supplied to Attenuators 7 and 9 are connected to booster 8
and 10 to an appropriate value, and the signal level of the television receiver output terminal 14 to an appropriate value.

In such a booster mixer 1, a part of the signal from the RF modulator 12 is transferred from the mixer 11→
There is a risk that it will leak along the route from the booster 8 to the filter 4, be guided to the antenna 2, and be radiated into the air, resulting in interfering radio waves. The boosters 5, 8, and 10 also have the role of suppressing such leakage. This is because boosters, or amplifiers, are generally non-reciprocal, amplifying the signal from the input side to the output side, but acting as an attenuator from the output side to the input side.

Similarly, when a video tape recorder (VTR) is connected to the recording output terminal 19, leakage of local oscillation signals from the tuner of the VTR to the antenna input terminal 3 occurs. The attenuator 16 and booster 17 are intended to suppress this leakage, but may be omitted depending on the performance of the tuner used.

In this booster mixer 1, leakage of a signal from the RF modulator 12 to the antenna input terminal 3 will be considered. The level of this leakage signal
In order to keep it below the FTZ or FCC regulation value,
The isolation from the modulator input terminal 13 to the antenna input terminal 3 must be 60 dB or more.

Normally, the signal level of the TV receiver output terminal 14 is several times higher than the signal level of the antenna input terminal 3.
dB, so in the booster mixer shown in FIG. 1, the gain per booster stage is about 0 to 1 dB. The isolation per stage of a conventional booster is about 20 dB when an attenuator is inserted in the previous stage and the gain is set to 0 dB. Therefore, in order to achieve an isolation of 60 dB or more from the modulator input terminal 13 to the antenna input terminal, it is necessary to provide three or more stages of boosters. This reduces the cost of booster mixers,
There were certain limits to miniaturization.

The purpose of this invention is to solve the above problems,
The object of the present invention is to provide a booster with good isolation, that is, a high frequency amplifier.

The high frequency amplifier of the present invention includes a first capacitor for frequency characteristic correction coupled between an input terminal and an input ground terminal, and a second capacitor for frequency characteristic correction coupled between an output terminal and an output ground terminal. a high frequency amplification circuit having a high frequency amplifier circuit, a connection wiring path connecting the ground side terminals of the first and second frequency characteristic correction capacitors, and a ground wiring connecting the input side ground terminal and the output side ground terminal. road and
a printed wiring board having a wiring path that connects the connection wiring path and the ground wiring path and forms an inductance; an equivalent circuit viewed from the output terminal to the input terminal includes a wiring path that forms the inductance; This feature is characterized in that a bridge-type trap circuit is formed by interposing the trap circuit.

The present invention will be explained below based on the drawings. FIG. 2 shows a circuit diagram of the high frequency amplification circuit arranged on the printed wiring board of the high frequency amplifier of the present invention. In the figure, 20
21 is an input terminal, 22 is an output terminal, 23 is an output ground terminal, 24 is a power supply voltage terminal, and 25 is a transistor. 26, 27, 2
8 and 29 are bias resistors, 30 are feedback resistors,
31 is a load resistor, 32 and 33 are DC cutoff capacitors, 34 and 35 are bypass capacitors, and 36
is a capacitor, 37 is a coil, and 38 is a chiyoke coil. The above shows the basic circuit configuration as an amplifier, and each circuit element is set to an optimal value so that it functions as a wideband amplifier. Further, high frequency characteristic correction capacitors 39 and 40 are added to this high frequency amplifier circuit to constitute a trap circuit together with a printed wiring board to be described later.

FIG. 3 shows an equivalent circuit of the high frequency amplifier circuit shown in FIG. 41 basic circuit parts as an amplifier
Expressed as follows, it becomes a simple circuit in which high-frequency characteristic correction capacitors 39 and 40 are provided between input side terminals 20 and 21 and between output side terminals 22 and 23, respectively.

FIG. 4 is a diagram showing a printed pattern of a printed wiring board 42 on which the high frequency amplification circuit shown in FIG. 2 is arranged. Each circuit element disposed on the printed wiring board is also illustrated, and each of these circuit elements is designated by the same reference numeral as in FIG. 2. In the figure, the transistor 25 is arranged in the broken line portion. This printed wiring board 42 has a wiring path 4.
3, 44, 45, 46, 47, 48, 49, 5
0,51 are provided. Furthermore, a bias resistor 26, a high frequency characteristic correction capacitor 39, a bypass capacitor 35, a bias resistor 28,
High frequency characteristic correction capacitor 40, load resistor 31
A wiring path 52 connecting each ground side terminal of
and a wiring path 53 that connects the input side ground terminal 21, the output side ground terminal 23, and the ground side terminal of the capacitor 36. The wiring paths 52 and 53 are connected by a wiring path 54, which is configured to exhibit inductance at high frequencies.

FIG. 5 shows an equivalent circuit of a high frequency amplifier composed of the high frequency amplifier circuit shown in FIG. 2 and the printed wiring board shown in FIG. 4. Basic amplification circuit section 41
can be regarded as an impedance with a large resistance component when viewed from the output side to the input side. This equivalent circuit is generally the same as a bridge T-type trap circuit used in a video intermediate frequency amplification circuit of a television receiver.

Therefore, when the high frequency amplifiers shown in FIGS. 2 and 4 are viewed from the output side to the input side, they form a trap circuit, and isolation is further increased due to the absorption and attenuation effect of the trap circuit.

FIG. 6 shows a booster mixer 55 using the high frequency amplifier of the present invention. This booster mixer has two stages of high frequency amplifiers 56 and 57. Circuit elements that are the same as those shown in FIG. 1 are designated by the same reference numerals. High frequency amplifier 5
6 and 57 high frequency characteristic correction capacitor 39
and 40 are adjusted to match the absorption/attenuation frequency to the frequency band of the RF modulator 12.

The measured value of the isolation from the modulator input terminal 13 to the antenna input terminal 3 of this booster mixer 55 is shown in FIG. 7 in comparison with the measured value of a booster mixer using a conventional high frequency amplifier. Curve 58 represents booster mixer 5 shown in FIG.
Curve 59 shows the isolation of a booster mixer using two stages of conventional high frequency amplifiers, and curve 60 shows the isolation of a booster mixer using three stages of conventional high frequency amplifiers. .

In the applicable frequency range around 600 MHz, the isolation of the booster mixer using the high frequency amplifier of the present invention increases rapidly, and the isolation is below -60 dB.
Meets FTZ regulation values. On the other hand, conventional booster mixers with two stages of high-frequency amplifiers do not meet the regulation value, and in order to meet the regulation value, it is necessary to
There must be steps.

As is clear from the above, according to the high frequency amplifier of the present invention, isolation from the output side to the input side can be increased. Therefore, if the high frequency amplifier of the present invention is used in a booster mixer, the conventional high frequency amplifier Since the required amplifier can be reduced to two stages, the cost of the booster mixer can be reduced and it can be made smaller. Furthermore,
Since the number of amplifiers can be reduced, the noise figure can be improved. Furthermore, it is clear that the high frequency amplifier of the present invention can be applied not only to booster mixers but also to devices requiring isolation.

[Brief explanation of the drawing]

Figure 1 is a diagram showing a booster mixer using a conventional high frequency amplifier, Figure 2 is a diagram showing a circuit of the high frequency amplifier of the present invention, Figure 3 is a diagram showing an equivalent circuit of the circuit in Figure 2, and Figure 4 is a diagram showing an equivalent circuit of the circuit in Figure 2. The figure shows a printed wiring board on which the circuit of Fig. 2 is arranged, Fig. 5 shows an equivalent circuit of a high frequency amplifier consisting of the circuit of Fig. 2 and the printed wiring board of Fig. 4, and Fig. The figure shows a booster mixer using the high frequency amplifier of the present invention.
FIG. 7 is a diagram showing a comparison between the measured isolation values of the booster mixer shown in FIG. 6 and the isolation of a booster mixer using a conventional high frequency amplifier. In the figure, 3 is an antenna input terminal, 4 is a filter,
6 is a distributor, 7 and 18 are attenuators, 11 is a mixer, 12 is an RF modulator, 13 is a modulator input terminal, 14 is an output terminal for a television receiver, 1
9 is an output terminal for recording, 20 is an input terminal, 21 is an input side ground terminal, 22 is an output terminal, 23 is an output side ground terminal, 39 and 40 are capacitors for high frequency characteristic correction, 42 is a printed wiring board, 52, 53 ,5
4 is a wiring path, 55 is a booster mixer, and 56 and 57 are high frequency amplifiers, respectively.

Claims (1)

[Claims for Utility Model Registration] A first capacitor for frequency characteristic correction coupled between an input terminal and an input grounding terminal, and a first capacitor for frequency characteristic correction coupled between an output terminal and an output grounding terminal. a high-frequency amplifier circuit having two capacitors, and a connection wiring path connecting the ground side terminals of the first and second frequency characteristic correction capacitors, and connecting the input side ground terminal and the output side ground terminal. a printed wiring board having a ground wiring path; and a wiring path that connects the connection wiring path and the ground wiring path and forms an inductance; an equivalent circuit viewed from the output terminal to the input terminal;
A high-frequency amplifier characterized in that a bridge-type trap circuit is formed by interposing a wiring path that forms the inductance.